Sensor controller, active pen, and communication method

ABSTRACT

A sensor controller, which is connected to sensor electrodes and detects positions of one or more active pens based on charge induced on the sensor electrodes, includes a processor and a memory. The memory stores instructions that, when executed by the processor, cause the sensor controller to: detect an approach of one of the one or more active pens using the sensor electrode; pair with the one of the one or more active pens with the approach of the one of the one or more active pens detected and update pairing state information indicative of a pairing state of each of the one or more active pens that is paired with the sensor controller; and transmit the pairing state information from the sensor electrodes to the one or more active pens via an uplink signal used as a reference for time synchronization.

BACKGROUND Technical Field

The present disclosure relates to a sensor controller, an active pen,and a communication method.

Background Art

A system is known that performs bidirectional communication and includesan active pen and a sensor controller that are paired. In a system ofthis type, the sensor controller transmits an uplink signal including anew local pen identifier (ID) and assigned communication configurationdata (frequencies, time slots, and the like allowed to be used fortransmission of downlink signals), and the active pen receives theuplink signal and returns a response. Pairing identified by the localpen ID is then established. After the pairing is established, the activepen utilizes the assigned communication configuration data to transmit adownlink signal.

U.S. patent application Ser. No. 2016/0246390 (hereinafter, PatentDocument 1) discloses an example of the system as described above.According to a technique in Patent Document 1, the sensor controller isconfigured to hold a quiet ID list. The quiet ID list is a list storinglocal pen IDs as described above. In a case where reception of adownlink signal from the paired active pen has been interrupted, thesensor controller stores, in the quiet ID list, the local pen IDassigned to the active pen. The local pen IDs stored in the quiet IDlist are sequentially assigned to new pairings in the chronologicalorder, oldest first.

However, the technique described in Patent Document 1 disadvantageouslydelivers degraded performance of the system due to a process formaintaining and managing the pairing state. This will be described belowin detail.

While consecutively receiving uplink signals, the active pen canrecognize whether the sensor controller still maintains the pairingstate with the active pen, based on whether each of the uplink signalsincludes a command directed to the active pen. However, when the activepen fails to receive uplink signals due to, for example, separation froma touch surface, the active pen may not recognize whether the sensorcontroller still maintains the pairing state with the active pen. As aresult, the next time the active pen transmits a downlink signal, theactive pen fails to determine whether the same communicationconfiguration data may be utilized for the transmission.

Thus, in a case of failing to receive an uplink signal at a timing whenthe active pen otherwise receives the uplink signal, the active penunilaterally cancels the pairing state, or subsequently whentransmitting a downlink signal, performs bidirectional communicationwith the sensor controller to check the pairing state. However,regardless of which of these processes is performed, inputting fails tobe immediately started at the time of next pen down, and the systemappears to a user to be delivering degraded performance. In particular,in a case where entrance to and exit from a coverage of uplink signalsfrequently occur within a short time such as in writing of characters,cancelation or check of the pairing state is performed each timeentrance or exit occurs. This causes the performance to appear to besignificantly degraded. Furthermore, one uplink signal allows only oneactive pen to be paired or checked, and thus, in a case where one sensorcontroller is simultaneously paired with a plurality of active pens(such a case is hereinafter referred to as “multi-pen”), the performanceappears to be further degraded.

BRIEF SUMMARY

Thus, an object of the present disclosure is to provide a sensorcontroller and an active pen capable of suppressing degradation ofperformance caused by a process for maintaining and managing the pairingstate.

Furthermore, in a case where the above-described multi-pen is used, theuser typically varies writing attributes (line color, line type, and thelike) for each active pen. Within the system, the writing attributes areassociated with the local pen IDs for management. However, the local penIDs are not notified to the user, and the appearances of the active pensare typically exactly the same. Thus, in the related art, the active penuser fails to find which writing attributes have been assigned to whichactive pens until the user actually writes with the active pens. This isinconvenient and has been desired to be improved.

Accordingly, another object of the present disclosure is to provide anactive pen allowing the user to easily recognize the writing attributesassigned to each active pen.

Additionally, in a case where two active pens with a matched global penID or a matched hash value of the global pen ID are present near onetouch surface, a situation may occur in which the two active pensestablish pairing with the sensor controller using the same local pen ID(conflict of pairing). In a case where the sensor controller has amethod for detecting a conflict, the conflict state can be avoided bytransmitting a command for pairing cancelation from the sensorcontroller to both active pens. However, this may induce breakage oflines being drawn.

Accordingly, another object of the present disclosure is to provide acommunication method, an active pen, and a sensor controller that canavoid a conflict of pairing without inducing breakage of lines beingdrawn.

A first aspect of the present disclosure provides a sensor controllerthat is connected to a plurality of sensor electrodes and detectspositions of one or more active pens based on charge induced on thesensor electrode, the sensor controller comprising a processor, and amemory storing instructions that, when executed by the processor, causethe sensor controller to: detect an approach of one of the one or moreactives pen using the sensor electrodes; pair with the one of the one ormore active pens with the approach of the one of the one or more activepens detected, and update pairing state information indicative of apairing state of each of the one or more active pens that is paired withthe sensor controller; and transmit the pairing state information fromthe sensor electrode to the one or more active pens via an uplink signalused as a reference for time synchronization.

A second aspect of the present disclosure provides an active pencommunicating with a sensor controller connected to a sensor electrode,the active pen including a pen tip electrode and an integrated circuitconnected to the pen tip electrode. The integrated circuit, inoperation, detects, via a coupling capacitance between the pen tipelectrode and the sensor electrode, an uplink signal including pairingstate information indicative of a pairing state of each of one or moreactive pens with which the sensor controller is paired, the one or moreactive pens including the active pen, and maintains or cancels thepairing state of the active pen based on the pairing state informationthat has been detected, and in a case where the pairing state of theactive pen is maintained, transmits a downlink signal configured basedon the pairing state of the active pen.

A third aspect of the present disclosure provides an active pencommunicating with a sensor controller connected to a sensor electrode,the active pen including a pen tip electrode, an integrated circuitconnected to the pen tip electrode, and an indicator. The integratedcircuit, in operation, controls the indicator to cause the indicator toprovide display for identification of a local pen ID in a case where thelocal pen ID is indicated to the active pen by an uplink signaltransmitted by the sensor controller.

A fourth aspect of the present disclosure provides a communicationmethod performed between an active pen and a sensor controller, thecommunication method including causing the active pen to transmit adownlink signal including first identification data that distinguishesthe active pen from another active pen after the active pen has beenpaired with the sensor controller, and causing the sensor controller toreceive the downlink signal including the first identification data andtransmit an uplink signal including second identification data acquiredbased on the received first identification data that are received.

A fifth aspect of the present disclosure provides an active pen thatcontrols transmission of a downlink signal based on an uplink signaltransmitted from a sensor controller, the active pen including a pen tipelectrode; and an integrated circuit which, in operation, transmits adownlink signal including first identification data that distinguishesthe active pen from another active pen via the pen tip electrode basedafter the active pen has been paired with the sensor controller, and ina case where an uplink signal including second identification datacorresponding to the first identification data is received, controlstransmission of a next downlink signal via the pen tip electrode basedon the second identification data.

A sixth aspect of the present disclosure provides a sensor controllerthat detects an active pen, in which the active pen transmits, via a pentip electrode provided at a pen tip, a downlink signal including firstidentification data that distinguishes the active pen from anotheractive pen after the active pen has been paired with the sensorcontroller, the sensor controller is connected to a sensor electrodecapacitively coupled to the pen tip electrode, and the sensor controllerincludes a processor and a memory storing instructions that, whenexecuted by the processor, cause the sensor controller to: receive, viathe sensor electrode, the downlink signal including the firstidentification data, and transmit an uplink signal including secondidentification data acquired based on the first identification data thatare received.

According to the first aspect of the present disclosure, the pairingstate information is broadcasted by the uplink signal to all of the oneor more active pens that are paired with the sensor controller, thepairing state information being indicative of the pairing state of eachof the active pens. Each of the active pens can thus recognize, byseeing the pairing state information, whether pairing with the activepen is maintained in the sensor controller. This eliminates a need forunilateral cancelation of the pairing state and bidirectionalcommunication for a check on the pairing state, enabling suppression ofdegradation of performance caused by a process for maintaining andmanaging the pairing state.

According to the third aspect of the present disclosure, each of theactive pens provides the display for the identification of the local penID. This allows the user to easily recognize the writing attributesassigned to each active pen.

According to the fourth aspect of the present disclosure, even in a casewhere two active pens with the matched global pen ID or the matched hashvalue of the global pen ID are present near one touch surface, aconflict of pairing can be avoided without inducing breakage of linesbeing drawn.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a general configuration of a positiondetecting system according to a first embodiment of the presentdisclosure;

FIG. 2 is a diagram illustrating an internal configuration of an activepen;

FIG. 3 is a diagram illustrating coverages of an uplink signal and adownlink signal;

FIG. 4 is a diagram illustrating a structure of a frame used to transmitand receive the uplink signal and the downlink signal;

FIGS. 5A, 5B, and 5C are diagrams illustrating types of the uplinksignal transmitted by the sensor controller;

FIG. 6 is a state transition diagram of the sensor controller;

FIG. 7 is a state transition diagram of the active pen;

FIG. 8 is a sequence diagram of operations of the sensor controller andthe active pen;

FIGS. 9A, 9B, and 9C are diagrams illustrating types of an uplink signaltransmitted by a sensor controller according to a second embodiment ofthe present disclosure; and

FIG. 10 is a sequence diagram of operations of the sensor controller andan active pen.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described below in detailwith reference to the attached drawings.

FIG. 1 is a diagram illustrating a general configuration of a positiondetecting system 1 according to a first embodiment of the presentdisclosure. As illustrated in FIG. 1, the position detecting system 1includes a plurality of active pens 2 a to 2 e and a position detectingdevice 3 with a touch surface 3 t. In the description below, in a casewhere the active pens 2 a to 2 e need not be distinguished from oneanother, the active pens 2 a to 2 e may be collectively referred to asthe active pen 2.

The active pen 2 is, for example, an electronic pen corresponding to anactive capacitive method and is configured to be capable ofcommunicating bidirectionally with the position detecting device 3.

FIG. 2 is a diagram illustrating an internal configuration of the activepen 2. As illustrated in FIG. 2, the active pen 2 includes a lead 20, apen tip electrode 21, a pen pressure detector 22, a switch 23, anindicator 24, a power supply 25, and an integrated circuit 26.

The pen tip electrode 21 is a conductor provided near the lead 20 and iselectrically connected to the integrated circuit 26 by wiring. The pentip electrode 21 is configured to be capacitively coupled to each of aplurality of sensor electrodes 30X and 30Y described below. The penpressure detector 22 is a functional unit that detects a force (penpressure) applied to a tip of the lead 20 (pen tip). Specifically, thepen pressure detector 22 is in abutting contact with a tail end of thelead 20. The pen pressure detector 22 is configured to detect, throughthe abutting contact, the force applied to the lead 20 when a userpresses the pen tip of the active pen 2 against the touch surface 3 t ofthe position detecting device 3. In a specific example, the pen pressuredetector 22 includes a variable capacitance module having a capacitancevarying according to a force applied to the pen tip.

The switch 23 is provided on a side surface of the active pen 2 and canbe turned on and off by the user. The indicator 24 is a device providinga display allowing the user to identify a local pen ID applied to theactive pen 2 by an uplink signal US described below. The indicator 24includes, for example, a light emitting diode (LED) number displayconfigured to be capable of displaying numbers or a LED configured to becapable of displaying a plurality of types of colors. The power supply25 is configured to supply operating power (direct current (DC) voltage)to the integrated circuit 26 and includes, for example, a cylindricalAAAA battery.

The integrated circuit 26 is a processing unit including a group ofcircuits formed on a substrate (not illustrated) and is connected toeach of the pen tip electrode 21, the pen pressure detector 22, theswitch 23, and the indicator 24. Processes described below and performedby the active pen 2 are all performed by the integrated circuit 26.

The integrated circuit 26 is configured to be capable of transmittingand receiving signals to and from the position detecting device 3 usingthe pen tip electrode 21. Among the thus transmitted and receivedsignals, signals transmitted from the position detecting device 3 to theactive pen 2 are referred to as uplink signals US, and signalstransmitted from the active pen 2 to the position detecting device 3 arereferred to as downlink signals DS.

The uplink signal US is typically a signal including a commandindicative of contents of control of the active pen 2. In the presentembodiment, the uplink signal US serves to broadcast, to all of one ormore active pens paired with the sensor controller, pairing stateinformation indicative of a pairing state of each of the active pens.The uplink signal US will be described below in detail with reference toFIGS. 5A, 5B, and 5C. Furthermore, a downlink signal DS is a signalincluding a burst signal corresponding to an unmodulated carrier signaland a data signal corresponding to a carrier signal modulated by apredetermined data. The integrated circuit 26 acquires data to betransmitted, in accordance with the command included in the uplinksignal US, and modulates the carrier signal using the acquired data, totransmit the data signal. Data transmitted by the data signal includespen pressure detected by the pen pressure detector 22, informationindicative of an on/off state of the switch 23, and a global pen ID ofthe active pen 2. The global pen ID is, unlike the local pen ID,information uniquely assigned to all the active pens 2 and is writteninto the integrated circuit 26 while the active pens 2 are beingmanufactured.

FIG. 3 is a diagram illustrating coverages of the uplink signal US andthe downlink signal DS. A zone A illustrated in FIG. 3 is specified asfollows: when the pen tip electrode 21 of the active pen 2 is located inthe zone A, the active pen 2 can receive the uplink signal UStransmitted by a sensor controller 31, and the sensor controller 31 canreceive the downlink signal DS transmitted by the active pen 2. In anexample in FIG. 3, active pens 2 c, 2 d, and 2 e are located in a zoneA.

The zone B is specified as follows: when the pen tip electrode 21 of theactive pen 2 is located in the zone B, the active pen 2 can receive theuplink signal US transmitted by the sensor controller 31, whereas thesensor controller 31 fails to receive the downlink signal DS transmittedby the active pen 2. The zone B is formed because the coverage of theuplink signal US is larger than the coverage of the downlink signal DSas illustrated in FIG. 3. In the example in FIG. 3, the active pens 2 band 2 f are located in the zone B.

The zone C is specified as follows: when the pen tip electrode 21 of theactive pen 2 is located in the zone C, the active pen 2 fails to receivethe uplink signal US transmitted by the sensor controller 31 and thesensor controller 31 also fails to receive the downlink signal DStransmitted by the active pen 2. In the example in FIG. 3, the activepens 2 a and 2 g are located in the zone C.

Thus, the area over the touch surface 3 t of the position detectingdevice 3 is classified into the zone A, the zone B, and the zone C inorder of increasing distance from the touch surface 3 t.

FIG. 4 is a diagram illustrating a structure of a frame used to transmitand receive the uplink signal US and the downlink signal DS. Asillustrated in FIG. 4, the uplink signal US and the downlink signal DSare transmitted and received in units of frames. The frame is, forexample, a display period for one screen of a display 33 (describedbelow) included in the position detecting device 3. The uplink signal USis typically transmitted at a head of the frame and serves to notify theactive pen 2 of a frame start timing (serves as a reference for timesynchronization). The uplink signal US may be transmitted a plurality oftimes within one frame.

A transmission time for the downlink signal DS within the frame isdivided into n time slots. Each time slot has a duration of Yμ seconds,and after the uplink signal US is transmitted, the divisional downlinksignals DS are arranged within the frame at intervals of Xμ seconds.During a period of Xμ seconds when transmission of the downlink signalDS is not performed, the following are performed: a display operation bythe display 33 described below, a finger position detecting operation bythe sensor controller 31 described below, and the like. Within each timeslot, the downlink signal DS with a predetermined number of symbols issimultaneously transmitted by a plurality of active pens 2.

The position detecting device 3 is configured to assign differentcombinations of frequencies and time slots to the respective active pens2 paired with the sensor controller 31. Each of the active pens 2 usesthe assigned combination of frequencies and time slots to transmit thedownlink signal DS. This enables a plurality of active pens 2 totransmit the downlink signal DS within the same frame.

Referring back to FIG. 1, the position detecting device 3 is a deviceconfigured to be capable of detecting the position of each active pen 2within the touch surface 3 t. The position detecting device 3 istypically a computer such as a tablet terminal, and a display surface ofthe display corresponds to the touch surface 3 t. However, the positiondetecting device 3 may be a digitizer with no display surface. In thedescription below, the position detecting device 3 is assumed to be atablet terminal.

The position detecting device 3 includes a sensor 30 disposedimmediately below the touch surface 3 t, the sensor controller 31, ahost processor 32 controlling the functions of units of the positiondetecting device 3 including the touch surface 3 t and the controller31, and the display 33 disposed below the sensor 30.

The sensor 30 constitutes a mutual-capacitance touch sensor and includesa plurality of sensor electrodes 30X and a plurality of sensorelectrodes 30Y arranged in a matrix. The plurality of sensor electrodes30X include a plurality of linear conductors extending in an illustratedY direction and arranged at regular intervals in an X directionorthogonal to the Y direction. Furthermore, the plurality of sensorelectrodes 30Y include a plurality of linear conductors extending in theX direction and arranged at regular intervals in the Y direction. FIG. 1illustrate only some of the plurality of sensor electrodes 30X and 30Y.The plurality of the sensor electrodes 30Y may also serve as commonelectrodes of the display 33, and in this case, the position detectingdevice 3 is referred to as an “in-cell type.” In contrast, the positiondetecting device 3 with the common electrodes in the display providedseparately from the sensor electrodes 30X and 30Y is referred to as, forexample, an “out-cell type” or an “on-cell type.” In the descriptionbelow, the position detecting device 3 is of the in-cell type.

The sensor controller 31 is a device connected to each of the pluralityof sensor electrodes 30X and 30Y to detect positions of one or moreactive pens 2 depending on charge induced on the sensor electrodes 30Xand 30Y. In one or more embodiments, the sensor controller 31 includes aprocessor and a memory storing instructions that, when executed by theprocessor, cause the sensor controller 31 to perform the functionsdescribed herein. Specifically, the sensor controller 31 includes afunction to detect an indicated position of each active pen 2 on thetouch surface 3 t and receive data transmitted by each active pen 2using the downlink signal DS, and a function to detect a position of thefinger on the touch surface 3 t. In a case where the position detectingdevice 3 is of the in-cell type, the sensor controller 31 also includesa function to apply, to the plurality of sensor electrodes 30Y, a commonpotential needed for the display operation of the display 33 (drivingoperation for pixel electrodes).

The sensor controller 31 includes, for the active pen 2, a function totransmit the uplink signal US toward each active pen 2 and receive thedownlink signal DS transmitted by each active pen 2, through the sensor30. In a case where the burst signal in the downlink signal DS isreceived, the sensor controller 31 derives the indicated position of theactive pen 2 based on a reception level of the burst signal at each ofthe sensor electrodes 30X and 30Y, and reports the indicated position tothe host processor 32. Furthermore, in a case where the data signal inthe downlink signal DS is received, the sensor controller 31 demodulatesthe data signal to retrieve data transmitted by the active pen 2 andreports the data to the host processor 32.

The host processor 32 is a central processing unit controlling theentirety of the position detecting device 3. Various applications suchas a drawing application and a communication application are operativelyconfigured on the host processor 32. The drawing application serves togenerate and store ink data indicative of a trace of the active pen 2 orthe finger on the touch surface 3 t based on a sequence of positions ofthe active pen 2 or the finger sequentially reported by the sensorcontroller 31 and to render the stored ink data. The drawing applicationalso controls the line width, transparency, line color, and the like ofthe ink data to be rendered, in accordance with the reported data, in acase where a report of the data transmitted from the active pen 2 isreceived from the sensor controller 31. The host processor 32 furthercontrollably rewrites display contents of the display 33 on aframe-by-frame basis. The display contents of the display 33 include animage resulting from the rendering.

FIGS. 5A, 5B, and 5C are diagrams illustrating types of the uplinksignal US transmitted by the sensor controller 31. As illustrated inFIGS. 5A, 5B, and 5C, the uplink signal US includes three types, type 1to type 3. The sensor controller 31 appropriately uses these types tocontrol the active pens 2.

The type 1 uplink signal US illustrated in FIG. 5A is a signalbroadcasted to all the active pens 2 in order to detect approach of eachof the active pens 2. The type 1 uplink signal US includes an uplinksignal type flag 1, frame structure information, communicationconfiguration data, and pairing state information.

The uplink signal type flag 1 is a flag allowing the active pen 2 todistinguish the type 1 uplink signal US from the type 2 and 3 uplinksignals US. In the type 1 uplink signal US, the uplink signal type flag1 is set to “0.” Accordingly, the uplink signal type flag 1 of “0”constitutes address information indicating that the signal is to betransmitted to all the active pens 2.

The frame structure information is information indicative of thestructure of the frame identified by a duration of the frame, a positionof the uplink signal US within the frame, specific durations of Xμseconds and Yμ seconds illustrated in FIG. 4, a number of time slotsincluded in the frame, a set of available frequencies, and the like.Specific frame structure information includes identification informationindicative of one of a plurality of structures preliminarily sharedbetween the active pen 2 and the sensor controller 31.

The communication configuration data is data indicative of a combinationof frequencies and time slots assigned to the active pen 2 with whichthe sensor controller 31 is to communicate. Specific communicationconfiguration data includes identification information indicative of oneof a plurality of combinations preliminarily shared between the activepen 2 and the sensor controller 31.

The pairing state information is information indicative of the pairingstate of each of one or more active pens 2 with which the sensorcontroller 31 is paired. The pairing state information includes apairing flag indicating whether the sensor controller 31 is paired withthe active pen 2, for each local pen ID (LPID) assigned to each activepen 2 at the time of pairing. The pairing flag is information indicativeof “1” in a case where the corresponding local pen ID is assigned to anyof the active pens 2 and of “0” in a case where the corresponding localpen ID is assigned to none of the active pens 2. FIGS. 5A, 5B, and 5Cillustrate examples of the sensor controller 31 capable of beingsimultaneously paired with up to six active pens 2. In this case, sixlocal pen IDs of 1 to 6 are provided, and the pairing state informationincludes six pairing flags.

Here, the pairing state is one of a state where the pairing is completedand maintained or a state where pairing is not maintained. In the statewhere the pairing is completed and maintained, configurations aremaintained that are needed to enable the active pen 2 to supply signalsto the position detecting device 3. Needed configurations include aconfiguration regarding a communication channel (for example,frequencies or time slots) and a delivery state of communicationresources or parameters such as a grant state of a local pen ID. On theother hand, in the state where the pairing is not maintained, theconfigurations are not provided that are needed to enable the active pen2 to supply signals to the position detecting device 3.

The pairing state information in the type 1 uplink signal US furtherincludes a pairing enable/disable flag. The pairing enable/disable flagis indicative of “1” when the sensor controller 31 is enabled toestablish a new pairing and of “0” when the sensor controller 31 isdisabled to establish a new pairing. The sensor controller 31 sets thepairing enable/disable flag to “0” in a case where the sensor controller31 is paired with a maximum allowable number (six in the example inFIGS. 5A, 5B, and 5C) of active pens 2 and otherwise to “1.”

Among the active pens 2 having received the type 1 uplink signal US, theactive pens 2 not paired with the sensor controller 31 yet firstreference the pairing enable/disable flag. In a case where the pairingenable/disable flag is set to “1,” these active pens 2 temporarilystore, in a memory (not illustrated), the frame structure information,communication configuration data, and pairing state information includedin the received uplink signal US. The active pens 2 also use thefrequencies and time slots indicated by the stored communicationconfiguration data to transmit the downlink signal DS including apairing request. The pairing request includes the above-described globalpen ID.

On the other hand, among the active pens 2 having received the type 1uplink signal US, the active pens 2 paired with the sensor controller 31each reference the pairing flag corresponding to the local pen IDassigned to the active pen 2. In a case where the pairing flag is set to“1,” these active pens 2 continuously maintain the pairing state. On theother hand, in a case where the pairing flag is set to “0,” the activepens 2 determine that the sensor controller 31 has canceled the pairingstate, and cancel the pairing state.

The type 2 uplink signal US illustrated in FIG. 5B is a signaltransmitted as a response to the downlink signal DS including a pairingrequest in order to pair with the active pen 2 with approach of theactive pen 2 detected. The type 2 uplink signal US includes an uplinksignal type flag 1, an uplink signal type flag 2, pairing target activepen information, and pairing state information. In the type 2 uplinksignal US, the uplink signal type flag 1 is set to “1.”

The uplink signal type flag 2 is a flag allowing the active pen 2 todistinguish the type 2 uplink signal US from the type 3 uplink signalUS. In the type 2 uplink signal US, the uplink signal US type flag 2 isset to “0.”

The pairing target active pen information includes the global pen IDincluded in the pairing request or a hash value of the global pen ID.Accordingly, the pairing target active pen information constitutesaddress information indicative of the active pen 2 to which the uplinksignal US is to be transmitted. The hash value constituting the pairingtarget active pen information is calculated by the sensor controller 31using a predetermined hash function preliminarily shared between thesensor controller 31 and each active pen 2.

The pairing state information in the type 2 uplink signal US is similarto the pairing state information in the type 1 uplink signal US exceptthe type 2 uplink signal US does not include a pairing enable/disableflag. However, in response to reception of the downlink signal DSincluding the pairing request, the sensor controller 31 determines thelocal pen ID to be assigned to the active pen 2 having transmitted thedownlink signal DS and updates, to “1,” the pairing flag correspondingto the determined local pen ID. This is a process for notifying theactive pen 2 of the local pen ID to be newly assigned.

In a case of receiving the type 2 uplink signal US, the active pen 2first determines whether the global pen ID or the hash value of theglobal pen ID included in the pairing target active pen informationbelongs to the active pen 2. In a case where it is determined that theglobal pen ID or the hash value belongs to the active pen 2, the activepen 2 compares the pairing state information in the last received andstored type 1 uplink signal US with the pairing state information in thecurrently received type 2 uplink signal US. As a result of thecomparison, the active pen 2 acquires and stores the local pen ID withthe corresponding pairing flag changed from “0” to “1,” in a memory (notillustrated) as the local pen ID assigned to this active pen 2. Theactive pen 2 also stores the temporarily stored frame structureinformation and communication configuration data in the memory (notillustrated). Thus, inside the active pen 2, the pairing state betweenthe active pen 2 and the sensor controller 31 is established.

The active pen 2, having established the pairing state, uses thefrequencies and time slots indicated by the stored communicationconfiguration data to transmit the downlink signal DS. The downlinksignal DS may include, for example, pen pressure. The sensor controller31 receives the thus transmitted downlink signal DS, and adds, to a listin the memory (not illustrated), information indicative of the activepen 2 having transmitted the downlink signal DS, to establish the stateof pairing with the active pen 2.

The type 3 uplink signal US illustrated in FIG. 5C is a signaltransmitted to control one of the one or more active pens 2 paired withthe sensor controller 31. The type 3 uplink signal US includes an uplinksignal type flag 1, an uplink signal type flag 2, a command, and pairingstate information. In the type 3 uplink signal US, the uplink signaltype flag 1 and the uplink signal type flag 2 are each set to “1.”

The command is information including the content of control of theactive pen 2 and the local pen ID indicative of the active pen 2 to becontrolled. The specific content of the control indicated by the commandincludes transmission of the pen pressure detected by the pen pressuredetector 22 or transmission of information indicative of an on/off stateof the switch 23.

In a case of receiving the type 3 uplink signal US, the active pen 2first determines whether the local pen ID assigned to the active pen 2is included in the command. In a case of determining the local pen ID tobe included in the command, the active pen 2 performs a processcorresponding to the content of the control indicated by the command.For example, in a case where the content of the control indicated by thecommand is transmission of the pen pressure detected by the pen pressuredetector 22, the active pen 2 acquires the latest pen pressure from thepen pressure detector 22 and includes the pen pressure in the downlinksignal DS for transmission.

FIG. 6 and FIG. 7 are each a state transition diagram of the sensorcontroller 31 and the active pen 2. With reference back to FIG. 4 andFIGS. 5A, 5B, and 5C, described above, in addition to FIG. 6 and FIG. 7,operations of the sensor controller 31 and the active pen 2 will bedescribed in further detail.

First, as seen in FIG. 6, the sensor controller 31 is configured tooperate in one of an uplink signal transmission state S0, other stateS1, and a downlink signal detection state S2. The uplink signaltransmission state S0 includes a normal state S0 a and a pairingin-execution state S0 b.

The sensor controller 31 is initially in the normal state S0 a. In thisstate, the sensor controller 31 transmits one of the type 1 uplinksignal US illustrated in FIG. 5A or the type 3 uplink signal USillustrated in FIG. 5C. In this case, the sensor controller 31 suitablytransmits type 1 uplink signals US while limiting the interval betweenthe uplink signals US to smaller than a certain value. This enables thesensor controller 31 to be paired, at an appropriate timing, with theactive pen 2 newly approaching the sensor controller 31.

In a case of receiving the downlink signal DS including the pairingrequest in response to the transmitted type 1 uplink signal US, thesensor controller 31 transits to the pairing in-execution state S0 b. Inthe pairing in-execution state S0 b, the sensor controller 31 transmitsthe type 2 uplink signal US. As a result, in a case of receiving thedownlink signal DS transmitted using the frequencies and time slotsindicated by the communication configuration data transmitted in thelast type 1 uplink signal US, the sensor controller 31 determines thatthe pairing has succeeded. The sensor controller 31 adds, to the list(not illustrated), information about the active pen 2 having transmittedthe downlink signal DS, to establish the pairing and returns to thenormal state S0 a. On the other hand, in a case of failing to receivesuch a downlink signal DS, the sensor controller 31 determines that thepairing has failed and returns to the normal state S0 a.

Once the sensor controller 31 completes transmission of the uplinksignal US, the sensor controller 31 temporarily transits to the otherstate S1 regardless of the type of the uplink signal US. In the otherstate 51, the sensor controller 31 performs an operation of detectingthe position of the finger or an operation for display on the display 33(specifically, application of the above-described common potential).While the sensor controller 31 is in the other state S1, the hostprocessor 32 illustrated in FIG. 1 may execute a part of rewrite controlof the display contents (for example, control for one gate line). In acase where Xμ seconds have elapsed since the transition to the otherstate S1, the sensor controller 31 transits to the downlink signaldetection state S2.

After transiting to the downlink signal detection state S2, the sensorcontroller 31 performs an operation of detecting, via the sensor 30illustrated in FIG. 1, the downlink signal DS transmitted by the activepen 2. In a case where Yμ seconds have elapsed since the transition tothe downlink signal detection state S2, the sensor controller 31 returnsto the other state Si to perform again the operation of detecting theposition of the finger or the operation for the display on the display33.

The sensor controller 31 repeats each of the other state Si and thedownlink signal detection state S2 n times. The sensor controller 31then returns to the uplink signal transmission state SO to transmit theuplink signal US.

As seen in FIG. 7, the active pen 2 is configured to operate in one of asleep state S0, a discovery state S1, a pairing in-execution state S2,an operation state S3, and a hold state S4.

The active pen 2 is initially in the sleep state S0. In this state, in acase of being powered on, the active pen 2 transits to the discoverystate S1. Furthermore, the active pen 2 in the sleep state SOcontinuously performs an operation of detecting occurrence of a touchoperation. In a case of detecting occurrence of a touch operation, theactive pen 2 also transits to the discovery state S1. The occurrence ofthe touch operation may be detected, for example, based on the penpressure detected by the pen pressure detector 22 exceeding apredetermined value or based on induction of charge on the pen tipelectrode 21.

In a case of being powered off, the active pen 2 in the discovery stateS1, returns to the sleep state S0. Furthermore, the active pen 2 in thediscovery state Si continuously performs the operation of detectingoccurrence of a touch operation. In a case of detecting no occurrence ofa touch operation for a given time, the active pen 2 returns to thesleep state S0. Also in this case, occurrence of a touch operation maybe detected, for example, based on the pen pressure detected by the penpressure detector 22 exceeding the predetermined value or based oninduction of charge on the pen tip electrode 21.

The active pen 2 in the discovery state S1 further performs an operationof detecting the uplink signal US via coupling capacitance between thepen tip electrode 21 and each of the plurality of sensor electrodes 30Xand 30Y. In a case where the type 1 uplink signal US is detected as aresult of the detecting operation, the active pen 2 transits to thepairing in-execution state S2. At this time, the active pen 2temporarily stores the frame structure information, communicationconfiguration data, and pairing state information included in thedetected uplink signal US as described above.

In the pairing in-execution state S2, the active pen 2 uses thefrequencies and time slots indicated by the stored communicationconfiguration data to transmit the downlink signal DS including thepairing request. The active pen 2 then performs the operation ofdetecting the uplink signal US, and in a case of detecting the type 2uplink signal US including the global pen ID of the active pen 2 or thehash value of the global pen ID, the active pen 2 acquires the local penID assigned to the active pen 2, from the pairing state informationincluded in the type 2 uplink signal US. The active pen 2 thenconfigures the local pen ID in the memory (not illustrated) in theintegrated circuit 26 along with the stored communication configurationdata, to establish the pairing state. The active pen 2 also controls theindicator 24 to cause the indicator 24 to provide display foridentification of the acquired local pen ID. The active pen 2subsequently transits to the operation state S3. On the other hand, in acase of failing to detect, within a predetermined time, the type 2uplink signal US including the global pen ID of the active pen 2 or thehash value of the global pen ID, the active pen 2 determines that thepairing has failed to return to the discovery state S1.

Each time the active pen 2, having transited to the operation state S3,receives the uplink signal US, the active pen 2 references the pairingstate information in the uplink signal US. The active pen 2 thusrecognizes that the pairing flag corresponding to the local pen ID ofthe active pen 2 is set to “1,” that is, that the sensor controller 31maintains the pairing with the active pen 2. Then, as long as the activepen 2 can recognize that the sensor controller 31 maintains the pairingwith the active pen 2, the active pen 2 maintains the operation state S3and transmits the downlink signal DS using the configuration based onthe pairing state (that is, using the frequencies and time slotsindicated by the stored communication configuration data). On the otherhand, in a case of recognizing that the pairing flag corresponding tothe local pen ID of the active pen 2 is set to “0” and that the sensorcontroller 31 does not maintain the pairing with the active pen 2, theactive pen 2 returns to the discovery state S1.

In the operation state S3, in a case where the uplink signal US is nolonger detected (for example, in a case where the active pen 2 has movedto the zone C in FIG. 3), the active pen 2 temporarily transits to thehold state S4 instead of immediately returning to the discovery stateS1. The hold state S4 is intended to maintain the pairing state for apredetermined time even after detection of the uplink signal US fails.The active pen 2 in the hold state S4 cancels the pairing state toreturn to the discovery state S1 in a case where detection of no uplinksignals US continues for a given period or in a case where, in spite ofsuccessful detection of the uplink signal US, the pairing stateinformation included in the uplink signal US allows the active pen 2 torecognize that the sensor controller 31 has canceled the state ofpairing with the active pen 2. At this time, the active pen 2 suspendsholding of the local pen ID and the communication configuration data andcontrols the indicator 24 to cause the indicator 24 to stop the displayfor identification of the local pen ID. On the other hand, in a casewhere, during the hold state S4, the pairing state information includedin the uplink signal US allows the active pen 2 to recognize that thesensor controller 31 maintains the pairing with the active pen 2, theactive pen 2 returns to the operation state S3.

FIG. 8 is a sequence diagram illustrating operations of the sensorcontroller 31 and the active pen 2. With reference to FIG. 8, operationsof the sensor controller 31 and the active pen 2 related to the pairingwill be described again below from a different viewpoint.

The sensor controller 31 transmits, in each frame, the type 1 uplinksignal US illustrated in FIG. 5A (S10 and S11). As illustrated in FIG.8, when the active pen 2 is assumed to receive the type 1 uplink signalUS in the frame 1 (S12), the active pen 2 transmits the downlink signalDS including the pairing request (S13). The pairing request includes theglobal pen ID as described above.

The sensor controller 31 receives the downlink signal DS including thepairing request (S14) and then transmits, in the next frame 2, the type2 uplink signal US illustrated in FIG. 5B (S15). As described above, thetype 2 uplink signal US includes the pairing target active peninformation indicative of the global pen ID or the hash value of theglobal pen ID included in the pairing request, and the pairing stateinformation with the pairing flag for the newly assigned local pen IDhaving changed from “0” to “1.”

The active pen 2 receives the type 2 uplink signal US, and then acquiresthe local pen ID assigned to the active pen 2, from the pairing stateinformation in the type 2 uplink signal US, and stores the local pen ID.The active pen 2 also stores the communication configuration dataincluded in the last received type 1 uplink signal US (S16). The activepen 2 subsequently uses the frequencies and time slots indicated by thestored communication configuration data to transmit the downlink signalDS (S17). As described above, the downlink signal DS includes the burstsignal and the data signal indicative of, for example, the pen pressuredetected by the pen pressure detector 22 illustrated in FIG. 2. Thesensor controller 31 receives the downlink signal DS and detects theposition of the active pen 2 based on the burst signal. The sensorcontroller 31 also acquires the pen pressure or the like from the datasignal, and outputs ink data as described above based on the result ofthe acquisition (S18).

As described above, according to the present embodiment, the pairingstate information is broadcasted by the uplink signal US to all of theone or more active pens 2 paired with the sensor controller 31, thepairing state information indicative of the pairing state of each of theactive pens 2. Each of the active pens can thus recognize, by seeing thepairing state information, whether pairing with the active pen ismaintained in the sensor controller 31. This eliminates a need forunilateral cancelation of the pairing state and bidirectionalcommunication for a check on the pairing state, enabling suppression ofdegradation of performance caused by a process for maintaining andmanaging the pairing state.

Furthermore, according to the present embodiment, each of the activepens 2 causes the indicator 24 illustrated in FIG. 2 to provide adisplay for identification of the local pen ID. Thus, the user caneasily recognize the writing attributes assigned to each active pen 2.

Now, the position detecting system 1 according to a second embodiment ofthe present disclosure will be described. The position detecting system1 according to the present embodiment differs from the positiondetecting system 1 according to the first embodiment in that the activepen 2 and the sensor controller 31 paired with each other transmit andreceive data (first and second identification data described below) toand from each other, the data being required to distinguish a pluralityof active pens 2 from each other. The position detecting system 1according to the present embodiment is otherwise similar to the positiondetecting system 1 according to the first embodiment, and thus,components of the present embodiment identical to the correspondingcomponents of the first embodiment are denoted by identical referencesigns, and in the description below, differences from the firstembodiment are focused on.

The present embodiment relates to avoiding a conflict of pairing thatmay occur in the position detecting system 1 according to the firstembodiment in a case where two active pens 2 with the matched global penID or the matched hash value of the global pen ID are present near onetouch surface 3 t. The object and general configuration of the presentdisclosure will first be described, and the present embodiment will thenbe described in detail.

First, it is assumed that two active pens 2 with the matched global penID or the matched hash value of the global pen ID approach the touchsurface 3 t while both active pens 2 are in an unpaired state and thatone of the active pens 2 is located in a zone A illustrated in FIG. 3,whereas the other active pen 2 is located in a zone B illustrated inFIG. 3. In this state, when the sensor controller 31 transmits the type1 uplink signal US (S11 in FIG. 8), the uplink signal US is received byboth two active pens 2. Then, each of the two active pens 2 transmitsthe downlink signal DS including the pairing request (S13 in FIG. 8).However, the downlink signal DS transmitted by the active pen 2 locatedin the zone B does not reach the sensor controller 31, and thus, thesensor controller 31 receives only one downlink signal DS. As a result,the sensor controller 31 transmits, as usual, the type 2 uplink signalUS including the global pen ID or the hash value of the global pen IDincluded in the downlink signal DS successfully received (S15 in FIG.8). The uplink signal US is received by both two active pens 2. Then,both two active pens 2 having transmitted the downlink signal DSdetermine that the global pen ID or the hash value of the global pen IDincluded in the received uplink signal US belongs to the active pens. Asa result, the two active pens 2 establish pairing with the sensorcontroller 31 via the same local pen ID. In other words, a conflict ofpairing occurs.

In a case where such a conflict of pairing occurs, the conflict statecan be avoided by transmitting a command for pairing cancelation fromthe sensor controller 31 to both active pens 2 in a case where thesensor controller 31 has a method for detecting a conflict. However,such pairing cancelation induces breakage of lines being drawn. Notethat the identical local pen ID precludes an operation in which only oneof the active pens 2 is instructed to cancel pairing with the sensorcontroller 31 by using the command transmitted by the sensor controller31. Additionally, in a case where the sensor controller 31 has no methodfor detecting a collision, cancelling pairing as described above isprevented, and the state of conflict of pairing continues until one ofthe active pens 2 moves away into a zone C illustrated in FIG. 3.

In addition, the continuing state of a conflict of pairing makes thedownlink signal DS transmitted by one of the active pen 2 noise to thedownlink signal DS transmitted by the other active pen 2, reducingdetection accuracy for the position of the active pen 2. Furthermore,the downlink signal DS not received by the sensor controller 31 has beenuselessly transmitted, thus also wastefully consuming power for theactive pens 2.

Thus, in the present embodiment, data required to distinguish the activepens 2 from each other (first identification data) is assumed to bearranged in the downlink signal DS. In a typical example, the firstidentification data is data indicating whether the pen tip is in contactwith the touch surface 3 t (contact state data). In the descriptionbelow, the first identification data is assumed to be contact statedata.

The sensor controller 31 receives, from the active pen 2, the downlinksignal DS including the first identification data, and then arranges thesecond identification data acquired based on the received firstidentification data, in the uplink signal US to be transmitted to theactive pen 2. The second identification data is, for example, datahaving the same contents as those of the first identification data.

The active pen 2 compares the thus received second identification datawith the first identification data transmitted by the active pen 2 todetermine whether the active pen 2 has been correctly detected by thesensor controller 31. Then, in a case where the active pen 2 isdetermined not to have been correctly detected, the active pen 2 cancelsthe pairing. Thus, for example, the pairing of the active pen 2 with thepen tip in contact with the touch surface 3 t is maintained, whereas thepairing of the active pen 2 being hovered (with the pen tip not incontact with the touch surface 3 t) is canceled, enabling a conflict ofpairing to be avoided without inducing breakage of lines being drawn. Asa result, the detection accuracy for the position of the active pen 2can be prevented from being reduced, and wasteful consumption of powerfor the active pen 2 can be prevented.

The object and general configuration of the disclosure according to thepresent embodiment have been described. Now, the configuration andoperation of the position detecting system 1 according to the presentembodiment will be described in detail. In the description below aswell, the first identification data is assumed to be contact state data.

FIGS. 9A, 9B, and 9C diagrams illustrating types of the uplink signal UStransmitted by the sensor controller 31 according to the presentembodiment. As illustrated in FIGS. 9A, 9B, and 9C, in the presentembodiment, the uplink signal US is also classified into three types,type 1 to type 3. Of the uplink signals US, the type 1 and the type 2uplink signals US are identical to the respective uplink signalsaccording to the first embodiment illustrated in FIGS. 5A and 5B. On theother hand, the type 3 uplink signal US is different from the uplinksignal according to the first embodiment illustrated in FIG. 5C in termsof the configuration of the pairing state information.

Specifically, pairing state information included in the type 3 uplinksignal US according to the present embodiment includes a data type flagand pairing data for each local pen ID. The data type flag is 1-bit dataindicative of the type of specific content of each pairing data. Thedata type flag is “0” when the pairing data is the pairing flagdescribed above, and the data type flag is “1” when the pairing data isthe second identification data described above. Thus, the type 2 andtype 3 uplink signals US with the data type flag of “1” are each asignal including the second identification data for each local pen ID(LPID). Note that the sensor controller 31 is configured to alternatelytransmit the type 3 uplink signal US with the data type flag of “0” andthe type 3 uplink signal US with the data type flag of “1” attransmission timings for the type 3 uplink signal US in a predeterminedratio (for example, 1:1).

Needless to say, the transmission ratio of the type 3 uplink signal USwith the data type flag of “0” to the type 3 uplink signal US with thedata type flag of “1” can be changed as appropriate. Depending on thepriorities of the uplink signals US, the transmission ratio may be setto, for example, “10:1.” Alternatively, in a case where the secondidentification data is contact state data, for example, the transmissiontimings for the type 3 uplink signal US with the data type flag of “1”may be limited to timings when the state of the active pen changes, suchas when the active pen comes into contact with the touch surface 3 t forthe first time after pairing with the sensor controller 31 or when theactive pen 2 subsequently comes into a hover state. This increases thetransmission frequency of the pairing flag with a high priority,enabling management of the pairing state to be optimized.

FIG. 10 is a sequence diagram of operations of the sensor controller 31and the active pen 2 according to the present embodiment. With referenceto FIG. 10, the operations of the sensor controller 31 and the activepen 2 related to the first and second identification data will bedescribed in detail. Note that, although not illustrated in FIG. 10, theacts described with reference to FIG. 8 and the like are actuallyperformed. Additionally, FIG. 10 illustrates the active pens 2 b and 2 dillustrated in FIG. 3 (the active pen 2 located in the zone B and theactive pen 2 with the pen tip in contact with the touch surface 3 t).Furthermore, FIG. 10 illustrates that a conflict of pairing describedabove is occurring between the active pens 2 b and 2 d (that is, theactive pens 2 b and 2 d store the same local pen ID).

First, when the sensor controller 31 transmits the uplink signal US(S30), each of the active pens 2 b and 2 d receives the uplink signal US(S31). Note that the uplink signal US may be of any one of the types 1to 3.

Here, the type 2 uplink signal US is a signal with the destination ofthe signal identified by the global pen ID or the hash value of theglobal pen ID, and the type 3 uplink signal US is a signal with thedestination of the signal identified by the local pen ID. However, forthe active pens 2 b and 2 d, these pieces of data all have an identicalvalue. Accordingly, even in a case where the uplink signal UStransmitted at S30 is the type 2 or type 3 uplink signal US, the uplinksignal US is received by both the active pens 2 b and 2 d at S31.

The active pens 2 b and 2 d, having received the uplink signal US atS31, reference the pen pressure detected by the pen pressure detector 22(see FIG. 2) to detect the contact state indicating contact of each pentip with the touch surface 3 t (S32). The contact state thus detected is“hover” for the active pen 2 b and “contact” for the active pen 2 d.Then, the downlink signal DS including the first identification dataindicative of the detected contact state is transmitted (S33).

Of the downlink signals DS transmitted by the active pens 2 b and 2 d atS33, the downlink signal DS transmitted by the active pen 2 b does notreach the sensor controller 31. This is because the active pen 2 b islocated in the zone B illustrated in FIG. 3. On the other hand, thedownlink signal DS transmitted by the active pen 2 d is received by thesensor controller 31.

The sensor controller 31, having received the downlink signal DSincluding the first identification data, extracts the firstidentification data from the downlink signal DS, and based on thefrequency and time slot used to transmit the downlink signal DS,acquires the local pen ID of the active pen 2 corresponding to thetransmission source (S34). Then, at the timing when the type 3 uplinksignal US with the data type flag of “1” illustrated in FIG. 9C is nexttransmitted, the second identification data acquired based on theextracted first identification data is set as pairing data for theacquired local pen ID. Accordingly, the type 3 uplink signal USincluding the second identification data is transmitted (S40). In thedescription below, the content of the second identification data isassumed to be identical to the content of the first identification dataextracted at S34.

The uplink signal US transmitted at S40 is received by both the activepens 2 b and 2 d as in the case of S31 (S41). The active pens 2 b and 2d, having thus received the uplink signal US, compare the secondidentification data included in the uplink signal US with the lasttransmitted first identification data (S42), and performs transmissioncontrol of the next downlink signal according to the result of thecomparison.

Specifically, the active pen 2 for which a match is found at S42 (inthis case, the active pen 2 d) repeats the process in S32 and thesubsequent acts. This maintains pairing with the active pen 2 d, and ina case where drawing is taking place, the drawing continues.

On the other hand, the active pen 2 for which a mismatch is found at S42(in this case, the active pen 2 b) performs a process for changing thepairing with the sensor controller 31 (S43). This process may be aprocess for temporarily canceling the pairing with the sensor controller31, in other words, a process for deleting the local pen ID andcommunication configuration data stored at S16 in FIG. 8 and returningto an unpairing state, or a process for changing, in the memory of theactive pen 2, the local pen ID stored at S16 in FIG. 8. In the lattercase, it is preferable that the changed local pen ID can be notifiedfrom the active pen 2 to the sensor controller 31. Additionally, theprocess for changing the pairing may be a process for stoppingtransmission of the downlink signal DS.

After performing S43, it is sufficient that the active pen 2 b waits forreception of the type 1 uplink signal US as usual. At this point intime, the active pen 2 d is in the paired state, and thus, the activepen 2 b performs pairing based on the type 1 uplink signal US receivedas a result of the wait, enabling pairing with the sensor controller 31to be established at least without causing a conflict with the activepen 2 d.

As described above, according to the position detecting system 1according to the present embodiment, in a case where the two active pens2 with the matched global pen ID or the matched hash value of the globalpen ID are present near one touch surface 3 t, one of the active pens 2(specifically, the active pen 2 in the hover state) can be exclusivelycaused to cancel pairing. Accordingly, a conflict of pairing can beavoided without causing breakage of lines being drawn. Additionally, thedetection accuracy for the position of the active pen 2 can be preventedfrom being reduced, and wasteful consumption of power for the active pen2 can be prevented.

The preferred embodiments of the present disclosure have been described.However, the present disclosure is not limited to such embodiments, andneedless to say, may be implemented in various manners without departingfrom spirits of the present disclosure.

For example, in the example described in each of the presentembodiments, the pairing state information including six pieces ofpairing data (pairing flag or second identification data) correspondingto respective local pen IDs of 1 to 6 is arranged in each uplink signalUS. However, one uplink signal US may include only a part of the pairingstate information such that uplink signals US including the pairingstate information including six pieces of pairing data corresponding torespective local pen IDs of 1 to 6 are transmitted alternately withuplink signals US including the pairing state information including sixpieces of pairing data corresponding to respective local pen IDs of 7 to12. This method is particularly suitable for a case where the uplinksignal US is transmitted a plurality of times within one frame (16.7milliseconds), for example.

Additionally, both the pairing flag and the second identification datamay be included in one uplink signal US. For example, the uplink signalUS may be used in which three pieces of pairing data corresponding tothe respective local pen IDs of 1 to 3 are the pairing flags, whereasthree pieces of pairing data corresponding to the respective local penIDs of 4 to 6 are the pieces of second identification data, or theuplink signal US may be used in which, in contrast, three pieces ofpairing data corresponding to the respective local pen IDs of 1 to 3 arethe pieces of second identification data, whereas three pieces ofpairing data corresponding to the respective local pen IDs of 4 to 6 arethe pairing flags.

Additionally, in the second embodiment described above, the firstidentification data is the contact state data. However, the firstidentification data can be configured using any other type of data aslong as the data is intended to distinguish the active pens 2 from eachother. For example, the pen pressure (for example, 256-level multileveldata) detected by the pen pressure detector 22 illustrated in FIG. 2 maybe treated as the first identification data. Additionally, the followingmay be treated as the first identification data: data (operation statedata) indicative of an operation state such as a depression state of theside switch provided on a housing of the active pen 2 or the tilt of theactive pen 2 which operation state may have different values dependingon how the human being grips the active pen 2; the data can berecognized by the sensor controller 31. Furthermore, in a case where theactive pen 2 can internally generate housing-unique temporally varyingdata (time-varying data), the time-varying data may be treated as thefirst identification data.

Additionally, in the second embodiment described above, the firstidentification data and the second identification data have identicalcontents. However, the contents of the first and second identificationdata need not necessarily be identical, and, for example, the secondidentification data may be configured using statistical data of last fewfirst identification data. In this case, the active pen 2 havingreceived the second identification data may acquire the statistical dataof the last few first identification data transmitted by the active penat S42 illustrated in FIG. 10 and compare the statistical data with thesecond identification data.

Additionally, in the second embodiment, the last transmitted firstidentification data is to be compared at S42. However, the firstidentification data may be newly acquired again immediately before S42(that is, the contact state may newly be detected), and the firstidentification data acquired as a result may be used for comparison atS42.

What is claimed is:
 1. A sensor controller that is connected to aplurality of sensor electrodes and detects positions of one or moreactive pens based on charge induced on the sensor electrodes, the sensorcontroller comprising: a processor; and a memory storing instructionsthat, when executed by the processor, cause the sensor controller to:detect an approach of one of the one or more active pens using thesensor electrodes; pair with the one of the one or more active pens withthe approach of the one of the one or more active pens detected, andupdate pairing state information indicative of a pairing state of eachof the one or more active pens that is paired with the sensorcontroller; and transmit the pairing state information from the sensorelectrodes to the one or more active pens via an uplink signal used as areference for time synchronization.
 2. The sensor controller accordingto claim 1, wherein the uplink signal includes address informationindicative of the one of the one or more active pen to which the uplinksignal is transmitted, and the pairing state information.
 3. The sensorcontroller according to claim 1, wherein the uplink signal includesaddress information indicating that the uplink signal is to betransmitted to all the one or more active pens, and the pairing stateinformation.
 4. An active pen communicating with a sensor controllerconnected to a sensor electrode, the active pen comprising: a pen tipelectrode; and an integrated circuit connected to the pen tip electrode,wherein the integrated circuit, in operation, detects via a couplingcapacitance between the pen tip electrode and the sensor electrode, anuplink signal including pairing state information indicative of apairing state of each of one or more active pens with which the sensorcontroller is paired, wherein the one or more active pens includes theactive pen, and maintains or cancels the pairing state of the active penbased on the pairing state information that has been detected, and in acase where the pairing state of the active pen is maintained, transmitsa downlink signal configured based on of the pairing state of the activepen.
 5. The active pen according to claim 4, wherein the integratedcircuit, in operation, maintains the pairing state for a predeterminedperiod after an attempted detection of the uplink signal US has failed,and transmits the downlink signal configured based on the pairing stateof the active pen in a case where the uplink signal is detected againwithin the predetermined period and where the pairing state informationin the uplink signal indicates that the sensor controller maintainspairing with the active pen.
 6. The active pen according to claim 4,wherein the integrated circuit, in operation, cancels the pairing stateof the active pen in a case where the pairing state information that hasbeen detected indicates that the sensor controller has canceled thepairing with the active pen.
 7. An active pen communicating with asensor controller connected to a sensor electrode, the active pencomprising: a pen tip electrode; an integrated circuit connected to thepen tip electrode; and an indicator, wherein the integrated circuit, inoperation, controls the indicator to cause the indicator to provide adisplay for identification of a local pen identifier in a case where thelocal pen identifier is indicated to the active pen by an uplink signaltransmitted by the sensor controller.
 8. The active pen according toclaim 7, wherein the integrated circuit, in operation, stores the localpen identifier for a predetermined period after an attempted detectionof the uplink signal has failed, and wherein the integrated circuit, inoperation, controls the indicator to cause the indicator to stop thedisplay for identification of the local pen identifier in a case wherestoring of the local pen identifier is suspended when the predeterminedperiod has elapsed.
 9. A communication method performed between anactive pen and a sensor controller, the communication method comprising:causing the active pen to transmit a downlink signal including firstidentification data that distinguishes the active pen from an otheractive pen after the active pen has been paired with the sensorcontroller; and causing the sensor controller to receive the downlinksignal including the first identification data and transmit an uplinksignal including second identification data acquired based on the firstidentification data that are received.
 10. The communication methodaccording to claim 9, further comprising: causing the active pen toreceive the uplink signal including the second identification data,compare the second identification data that are received with the firstidentification data, and control transmission of a next downlink signaldepending on a result of comparing the second identification data thatare received with the first identification data.
 11. The communicationmethod according to claim 10, wherein, in a case where, as the result ofcomparing the second identification data that are received with thefirst identification data, the active pen determines that the receivedsecond identification data matches the first identification data, theactive pen transmits the downlink signal including the firstidentification data that distinguishes the active pen from the otheractive pen, and in a case where, as the result of comparing the secondidentification data that are received with the first identificationdata, the active pen determines that the second identification data thatare received does not match the first identification data, the activepen performs a process that changes pairing with the sensor controller.12. The communication method according to claim 9, wherein the firstidentification data is contact state data indicating whether a pen tipof the active pen is in contact with a touch surface.